Laser irradiation apparatus and method of fabricating organic light emitting display using the same

ABSTRACT

Provided are a laser irradiation apparatus and method of fabricating an organic light emitting display using the same. The laser irradiation apparatus includes a mask positioned below the laser generator, and the mask is patterned such that lengths of an upper portion and a lower portion of a mask pattern are patterned longer than a length of a middle portion of the mask pattern with respect to the scanning direction. The method of fabricating an organic light emitting display includes scanning a laser beam on a predetermined region of the donor substrate using the laser irradiation apparatus to form an organic layer pattern on the substrate. When the organic layer pattern is formed using a laser induced thermal imaging (LITI) method, the transfer may be carried out using a laser beam having low energy, laser beam efficiency may be enhanced, the organic layer may be less damaged, and the quality of the organic layer pattern to be transferred may also be enhanced.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 11/020,670, filed on Dec. 27, 2004, and claims priority to andthe benefit of Korean Patent Application No. 2004-0075657, filed Sep.21, 2004, the disclosure of which are both incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a laser irradiation apparatus andmethod of fabricating an organic light emitting display using the sameand, more particularly, to a laser irradiation apparatus including amask in which a length of a middle portion of a mask pattern ispatterned to be longer than those of an upper portion and a lowerportion of the mask pattern on the basis of a scanning direction, andmethod of fabricating an organic light emitting display using the same

2. Description of the Related Art

In general, an organic light emitting display, which is a flat paneldisplay, includes an anode, a cathode, and organic layers between theanode and the cathode. The organic layers include at least an emissionlayer. The organic layers may further include a hole injection layer, ahole transport layer, an electron transport layer, and an electroninjection layer, in addition to the emission layer. The organic lightemitting display may be classified into a polymer organic light emittingdisplay and a small molecule organic light emitting display depending onthe organic layer, particularly, a material that forms the emissionlayer.

In order to realize a full color organic light emitting display, it isrequired to pattern the emission layer. A method of patterning theemission layer includes a method using a shadow mask in the smallmolecule organic light emitting display, and an ink-jet printing methodor a laser induced thermal imaging (hereinafter, referred to as LITI)method in the polymer organic light emitting display. With the LITImethod, it is possible to finely pattern the organic layer. The LITImethod is usable for a large-sized display and is advantageous in highresolution. Advantageously, the LITI method is a dry process, unlike theink-jet printing that is a wet process.

FIG. 1 is a cross-sectional view illustrating a method of forming anorganic layer pattern using an LITI method.

Referring to FIG. 1, a donor substrate 120 where an organic layer 130 isformed is laminated on a substrate 110 where a predetermined element isformed. When a laser beam 150 is irradiated on a predetermined region ofthe donor substrate 120 having the organic layer 130, the laser beam 150is absorbed by a light-to-heat conversion layer of the donor substrate120 and then converted to thermal energy, which allows the organic layer130 forming a transfer layer to be transferred onto the substrate 110,thus patterning the organic layer on the substrate 110. In this case,the organic layer 130 is separated from the donor substrate 120 by thethermal energy, and is transferred onto the substrate 110 while bondingwithin the organic layer 130 is broken. Energy required to break thebonding within the organic layer 130 should be higher than energyrequired to allow the organic layer 130 to be broken from the donorsubstrate 120 and transferred. Dotted portions indicate portions wherethe bonds within the organic layer 130 are broken.

FIGS. 2A to 2C are schematic views illustrating a method of fabricatingan organic light emitting display using a conventional laser irradiationapparatus.

Referring to FIG. 2A, a donor substrate 120 where an organic layer 130is formed is laminated on a substrate 110 where a pixel electrode isformed.

The laser irradiation apparatus 200 includes a laser generator 240, apatterned mask 260, and a projection lens 270. The laser generator 240irradiates a laser beam 250 on a predetermined region of the donorsubstrate 120, and performs scanning in an arrow direction. In thiscase, the laser beam 250 irradiated from the laser generator 240penetrates the patterned mask 260, and the penetrated laser beam 250 isfocused by the projection lens 270 and then irradiated on the donorsubstrate 120. The laser beam 250 is shielded from a portion where themask 260 is not patterned.

Referring to FIG. 2B, the laser beam 250 performs scanning on the donorsubstrate 120 including a region where the pixel electrode 210 isformed. An oblique line portion indicates a region 255 on which thelaser beam 250 performs scanning.

By means of the scanning of the laser beam 250, the organic layer 130 onthe donor substrate 120 is transferred onto the substrate 110 where thepixel electrode 210 is formed. After the transfer process, a cathode isformed on the organic layer pattern, thereby completing the fabricationof the organic light emitting display.

Referring to FIG. 2C, the amount of laser irradiated on a scanningregion while the laser beam is scanned is shown as a beam profile 280 ofthe laser beam 250 irradiated on the donor substrate 120. An x-axisindicates a region where the laser beam is scanned and a y-axisindicates energy of the laser beam. In particular, the amount of thelaser beam irradiated on the scanning region of the donor substrate 120is uniform. That is, it can be seen that the laser beam is uniformlyirradiated over the entire region of the donor substrate 120 where thelaser beam is irradiated. As shown in FIG. 1, energy required to breakthe bonding within the organic layer 130 should be higher than thatrequired for allowing the organic layer 130 to be separated from thedonor substrate 120 and transferred. As a result, energy required forbreaking the bonding within the organic layer 130 is applied in order totransfer the organic layer 130. That is, an excessive amount of energymay be applied to transfer the organic layer 130, which may cause theorganic layer to be damaged and the quality of the transferred organiclayer pattern to be degraded.

SUMMARY OF THE INVENTION

The present invention, therefore, solves aforementioned problemsassociated with the conventional art by providing a laser irradiationapparatus, which is capable of allowing an organic layer to betransferred, a damage of the organic layer to be reduced, and a qualityof a transferred organic layer pattern to be enhanced by means of alaser beam having low energy when the organic layer pattern is formedusing LITI method, and method of fabricating an organic light emittingdisplay using the same.

In an exemplary embodiment according to the present invention, a laserirradiation apparatus includes: a laser generator; and a mask positionedbelow the laser generator, wherein the mask is formed such that lengthsof an upper portion and a lower portion of a mask pattern are patternedlonger than a length of a middle portion of the mask pattern withrespect to the scanning direction. As a result, the organic layer may betransferred using a laser beam having low energy.

In addition, the apparatus may further include a projection lenspositioned below the mask.

In another exemplary embodiment according to the present invention, amethod of fabricating an organic light emitting display includes:providing a substrate where a pixel electrode is formed; laminating adonor substrate on a surface of the substrate, and scanning a laser beamon a predetermined region of the donor substrate using the laserirradiation apparatus to form an organic layer pattern on the substrate.

The organic layer pattern may be a single layer or a multi-layer of atleast two layers selected from a group consisting of an emission layer,a hole injection layer, a hole transport layer, an electron transportlayer and an electron injection layer.

The mask pattern may be formed to be a | shape. The shape of the maskpattern may be formed with at least one side being opened, preferably,may be formed as any one among

,

,

and

. Alternatively, the mask may be employed such that a center of themiddle portion of the mask pattern is not patterned, and the mask may bepatterned in various shapes.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will be describedin reference to certain exemplary embodiments thereof with reference tothe attached drawings in which:

FIG. 1 is a cross-sectional view illustrating a method of forming anorganic layer pattern using an LITI method;

FIGS. 2A to 2C are schematic views illustrating a method of fabricatingan organic light emitting display using a conventional laser irradiationapparatus;

FIG. 3 is a schematic view illustrating a laser irradiation apparatus inaccordance with the present invention;

FIGS. 4A to 4H are plan views of masks having various pattern shapesprovided in a laser irradiation apparatus in accordance with the presentinvention; and

FIGS. 5A to 5D are schematic views illustrating a method of fabricatingan organic light emitting display using a laser irradiation apparatus inaccordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Like numbers refer to like elementsthroughout the specification.

FIG. 3 is a schematic view illustrating a laser irradiation apparatus inaccordance with the present invention.

Referring to FIG. 3, a laser irradiation apparatus 300 includes a lasergenerator 340, a patterned mask 360 positioned below the laser generator340, and a projection lens 370. A beam shaping device may be furtherincluded between the laser generator 340 and the patterned mask 360which acts to make a laser beam irradiated from the laser generator 340uniform.

The mask 360 is formed such that lengths of an upper portion and a lowerportion of the mask pattern are patterned longer than a length of amiddle portion of the mask pattern on the basis of a scanning direction.A detail description will be made with reference to FIGS. 4A to 4H.

FIGS. 4A to 4H are plan views of masks having various pattern shapesprovided in a laser irradiation apparatus in accordance with the presentinvention.

Referring to FIGS. 4A and 4B, the mask is patterned to have a | shape.The mask pattern may be divided into an upper portion A, a lower portionB, and a middle portion C. With respect to a direction vertical to thescanning direction, a length of the middle portion C of the mask patternis formed longer than that of a region to be transferred when an organiclayer is formed using the LITI method.

The lengths a and b of the upper portion and the lower portion of themask pattern are patterned longer than a length c of the middle portionof the mask pattern on the basis of the scanning direction. Accordingly,when a laser beam is scanned as described later, an amount of laser beamenergy irradiated onto the upper portion A and the lower portion B ofthe mask pattern may be larger than an amount of the laser beam energyirradiated onto the middle portion C of the mask pattern.

A hatched portion 420 denotes a region where the laser beam is notpenetrated but blocked, and the laser beam penetrates the patternedregion 410 to be irradiated.

Three mask patterns are formed in the patterned mask 460. However, thisis just an illustrative example, and a required number of mask patternsmay be formed.

The mask pattern having an | shape as shown in FIG. 4B has the upperportion A and the lower portion B which are obliquely patterned. Theremaining structure is same as the mask pattern shown in FIG. 4A.

Referring to FIGS. 4C to 4F, at least one side of the mask is openedwhen seen from its plan view. Preferably, the mask is patterned to have

,

,

, or

shape.

Referring to FIGS. 4C and 4D, with respect to the scanning direction,the length c of the middle portion of the mask pattern is shorter thanthe lengths a and b of the upper and lower portions of the mask pattern,however, the mask pattern is formed such that one side of the middleportion C of the mask pattern is short to be

shaped and

shaped, respectively.

Referring to FIGS. 4E and 4F, with respect to the scanning direction,the summed length c of the middle portion of the mask pattern is shorterthan the lengths a and b of the upper and lower portions of the maskpattern so that the mask has a

shape or a

shape.

The rest of the structures are the same as the mask pattern shown inFIG. 4A.

Referring to FIGS. 4G and 4H, the center D of the middle portion C ofthe mask pattern is not patterned. With respect to the scanningdirection, the lengths a and b of the upper and lower portions of themask pattern are patterned longer than the summed length c of the middleportion of the mask pattern. The center D of the middle portion C of themask pattern is shown as a rectangle in FIG. 4G and as a lozenge in FIG.4H. The rest of the structures are the same as the mask pattern shown inFIG. 4A.

FIGS. 5A to 5D are schematic views illustrating a method of fabricatingan organic light emitting display using a laser irradiation apparatus inaccordance with the present invention.

Referring to FIGS. 5A and 5B, a donor substrate 120 where an organiclayer 130 is formed is laminated on a substrate 110 where a pixelelectrode is formed.

A laser irradiation apparatus 500 includes a laser generator 540, apatterned mask 560, and a projection lens 570. The laser generator 540irradiates a laser beam 550 onto a predetermined region of the donorsubstrate 120, and performs scanning in an arrow direction. In thiscase, the laser beam 550 irradiated from the laser generator 540penetrates the patterned mask 560, and is focused by the projection lens570 to be irradiated onto the donor substrate 120. The laser beam 550 isblocked from a portion where the mask 560 is not patterned.

When the scanning direction is a reference of the patterned mask 560,the lengths a and b of the upper and lower portions of the mask patternare longer than the length c of the middle portion of the mask pattern.

Referring to FIG. 5C, the laser beam 550 is scanned on the donorsubstrate 120 including the region where the pixel electrode 510 isformed. An oblique line portion indicates a region where the laser beam550 is scanned.

Scanning of the laser beam 550 allows the organic layer 130 on the donorsubstrate 120 to be transferred onto the substrate 110 where the pixelelectrode 510 is formed.

The process of forming the organic layer pattern may be carried out inan N₂ atmosphere. As the organic layer pattern to be transferred may beoxidized in an atmosphere containing oxygen, the transfer process may becarried out in the N₂ atmosphere where the oxygen component is removed.

In addition, the transfer process may be carried out in a vacuumatmosphere, which may advantageously suppress bubbles from occurringbetween the donor substrate and the substrate when a process oflaminating the donor substrate onto a surface of the substrate iscarried out.

The organic layer pattern may be a single layer or a multi-layer of atleast two layers selected from a group consisting of an emission layer,a hole injection layer, a hole transport layer, an electron transportlayer and an electron injection layer.

After the transfer process is carried out, a cathode is formed on theorganic layer pattern which is already formed, thereby completingformation of the organic light emitting display.

Referring to FIG. 5D, an amount of laser irradiated on a scanning regionwhile the laser beam performs scanning is shown as a beam profile 580 ofthe laser beam 550 irradiated on the donor substrate 120. An x-axisindicates a region where the laser beam is scanned and a y-axisindicates energy of the laser beam. To detail this, as the amount oflaser beam energy irradiated on the scanning region of the donorsubstrate 120 is not uniform, it can be seen that an energy amount ofthe laser beam 550 irradiated on the region scanned through the upperportion A and the lower portion B of the mask pattern is larger thanthat irradiated on the region scanned through the middle portion C ofthe mask pattern. The energy at the region scanned through the upperportion A and the lower portion B of the mask pattern is used to breakthe bonding within the organic layer 130, and the energy at the regionscanned through the middle portion C of the mask pattern is used toallow the organic layer 130 to separate from the donor substrate 120 andbe transferred.

As described with reference to FIG. 1, the energy required for breakingthe bonding within the organic layer 130 is higher than the energyrequired for allowing the organic layer 130 to be separated from thedonor substrate 120 and transferred.

Accordingly, when only energy required for allowing the organic layer130 separated from the donor substrate 120 and transferred is applied tothe donor substrate 120, the bonding within the organic layer 130 may bebroken and the organic layer 130 may be separated from the donorsubstrate 20 and transferred. That is, the organic layer pattern may beformed using a laser beam having low energy, which leads to anenhancement of the laser beam. In addition, the low energy is applied tothe organic layer, so that the organic layer pattern may be less damagedby the laser beam having the low energy.

According to the present invention as mentioned above, when the organiclayer pattern is formed using the LITI method, the mask is formed suchthat lengths of the upper and lower portions of the mask pattern areformed longer than the length of the middle portion of the mask patternwith respect to a scanning direction, and the laser beam is irradiatedthrough the mask. Accordingly, the organic layer may be transferredusing a laser beam having low energy, and the laser beam efficiency maybe enhanced. In addition, the organic layer may be less damaged, and thequality of the organic layer pattern to be pattern may also be enhanced.

Although the present invention has been described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that a variety of modifications and variations may bemade to the present invention without departing from the spirit or scopeof the present invention defined in the appended claims, and theirequivalents.

1. A method of fabricating an organic light emitting display,comprising: providing a substrate where a pixel electrode is formed;laminating a donor substrate on an entire surface of the substrate; andscanning a laser beam on a predetermined region of the donor substrateusing a laser generator and a mask positioned below the laser generatorto form an organic layer pattern on the substrate, wherein lengths of anupper portion and a lower portion of the mask are patterned longer thana length of a middle portion of the mask pattern with respect to ascanning direction.
 2. The method as recited in claim 1, wherein themask pattern has a I shape.
 3. The method as recited in claim 1, whereinthe mask pattern is shaped such that at least one side of the maskpattern is opened.
 4. The method as recited in claim 3, wherein the maskpattern is formed to have any one shape of

,

,

and

.
 5. The method as recited in claim 1, wherein the mask is patternedexcept a center of the middle portion of the mask pattern.
 6. The methodas recited in claim 1, wherein forming the organic layer pattern on thepixel electrode is carried out in a nitride (N₂) atmosphere.
 7. Themethod as recited in claim 1, wherein forming the organic layer patternon the pixel electrode is carried out in a vacuum atmosphere.
 8. Themethod as recited in claim 1, wherein the organic layer pattern is asingle layer or a multi-layer of at least two layers selected from agroup consisting of an emission layer, a hole injection layer, a holetransport layer, an electron transport layer and an electron injectionlayer.